1. Field of the Invention
The present invention relates in general to a recording head unit and a method of producing the recording head unit.
2. Discussion of Related Art
A recording head of a recording head unit generally includes an actuator unit having a plurality of individual electrodes which are provided to correspond respectively to a plurality of recording elements. The actuator unit is arranged such that, when an operating signal is supplied to selected one or ones of the plurality of individual electrodes, one or ones of the plurality of recording elements corresponding to the selected one or ones of the individual electrodes is/are operated to perform recording of suitable images, characters, etc., on a recording medium. As one example of such an actuator unit, a piezoelectric actuator is disclosed in U.S. Patent Application Publication No. 2003/0112298 A1 corresponding to JP-A-2003-69103 (FIGS. 2 and 3, in particular), for instance. The piezoelectric actuator includes a plurality of tabular piezoelectric elements and a plurality of individual electrodes (signal electrodes) which respectively correspond to the plurality of piezoelectric elements.
One example of such a piezoelectric actuator is shown in FIG. 12. In the piezoelectric actuator generally indicated at 100 in FIG. 12, a flexible printed wiring board 103 is electrically connected to a plurality of individual electrodes 102 formed on a surface of each piezoelectric element of the actuator. Since the flexible printed wiring board may be referred to as a flexible printed circuit, the flexible printed wiring board 103 is referred to as “FPC 103” in the following description. The FPC 103 has a three-layer structure consisting of a base film 104; a plurality of conductive leads 105 which respectively correspond to the plurality of individual electrodes 102 and each of which includes a wire portion 105a and a terminal portion 105b (electric bonding pad); and a cover coat 106 having an electric insulating property and covering the conductive leads 105. The plurality of conductive leads 105 constitute a wiring pattern. Portions of the cover coat 106 corresponding to the terminal portions 105b are partially removed, so that the terminal portions 105a are exposed to an outside, and a bump 107 is formed on the exposed portion of each terminal portion 105b. Each bump 107 includes a core 107a which is formed of a metal such as Ni and which protrudes toward the corresponding individual electrode 102, and a bonding agent 107b such as solder to cover the core 107a. For joining the piezoelectric actuator 100 and the FPC 103 to each other, with the bumps 107 held in contact with the respective individual electrodes 102 by pressing the bumps 107 onto the same 102, there is applied heat, pressure, or vibration to the contacting portions where the bumps 107 and the individual electrodes 102 are respectively held in contact with one another, thereby melting the bonding agents 107b. As a result, the terminal portions 105b of the FPC 103 and the individual electrodes 102 are electrically connected respectively to one another via the respective bumps 107.